Current air conditioning (HVAC) systems employ multi-pole relays encased in clear polycarbonate and resembling an oversize ice cube; thus the common name “ice cube” relays. The relays are typically mounted to the chassis or a board and have up to 11 single point connections configured with 0.25″×0.032″ male quick disconnect wiring terminals. As all of the terminals on the multi-pole relay are physically the same, i.e., male quick disconnect type, and the wires to be connected to the relay are all terminated with the same size female quick disconnects, this leads to the possibility of incorrect connection of the wires to the relay terminals during manufacturing, assembly and troubleshooting.
For example, the relays in question may have up to three poles with double throw and nine connectors to the internal relays with an additional two connectors for coil voltage. Thus, with 11 terminals and 11 wiring leads there are 11! (eleven factorial) ways to connect the wiring leads to the terminals. This can lead to errors in servicing the unit, which in turn can lead to a malfunction in the operation of the unit.